1. Field of the Invention
The present invention relates to an image capturing device, and more specifically, to an image capturing device capable of providing straight light-guiding paths and comprising a light-guiding component that is composed of opaque material(s).
2. Description of the Prior Art
Image capturing technologies are popularly applied to several kinds of electronic devices, such as an optical mouse, or a fingerprint recognition device. An optical mouse according to a prior art is herein taken as an example. The operation of the optical mouse is described as follows. In general, a light-emitting component of the optical mouse emits a light ray that will arrive at a surface of an object (i.e., a surface of a desk or a mouse pad). Next, a sensor of the optical mouse senses the light ray reflected by the surface to generate a corresponding image. In this way, when the optical mouse moves on the surface, the optical mouse can capture a plurality of images using image recognition technologies, and then compute a displacement vector between the optical mouse and the surface. Finally, the optical mouse can generate a pointing signal corresponding to the displacement vector and send the pointing signal to a host (i.e., a computer).
Please refer to FIG. 1. FIG. 1 is a cross-sectional diagram of an optical mouse 10 according to the prior art. The optical mouse 10 comprises a light-emitting component 12, a support 14, a transparent component 16, a lens 18, a mold 22, a sensor 24, a conducting support 26, a diaphragm 28, and a printed circuit board (PCB) 30. A lighting system according to the prior art is composed of the light-emitting component 12, the support 14 and the transparent component 16. An image formation system according to the prior art is composed of the lens 18 (installed in the transparent component 16), the mold 22, the sensor 24, the conducting support 26 and the diaphragm 28. For the lighting system, the light-emitting component 12 is a light emitting diode (LED) for emitting a light ray L1′ toward a surface 31 of an object. The support 14 is utilized for fixing the light-emitting component 12. The light ray L1′ emitted by the light-emitting component 12 is guided toward an image formation area of the surface 31 with an appropriate angle by the transparent component 16 through reflection and refraction, wherein the light ray L1′ is usually obliquely guided toward the image formation area of the surface 31.
For the image formation system, the conducting support 26 is utilized for fixing the sensor 24 and for supplying power to the sensor 24. The mold 22 is generated by an injection-molding process, where the material of the mold 22 is black plastic. The mold 22 is a container for protecting the sensor 24, and comprises a lower cover. The lower cover has a hole so that it can be utilized as a diaphragm 28. The diaphragm 28 is utilized for filtering out undesired light rays, in order to improve the quality of the optical image formation. In addition, the lens 18 is utilized for collecting and transmitting the reflective light rays on the surface 31 to the sensor 24. The PCB 30 transmits the plurality of images sensed by the sensor 24 and outputs the images to a control component (not shown in FIG. 1). The control component then generates a pointing signal according to the images. The PCB 30 can supply power to the sensor 24 and the light-emitting component 12, and can be connected to the conducting support 26 and the support 14 to assist in fixing the sensor 24 and the light-emitting component 12.
The optical mouse 10 has the following disadvantages, however:
(1) Through the transparent component 16, the angle of the light ray L1′ emitted by the light-emitting component 12 is changed and arrives obliquely at the surface 31, i.e. the light ray L1′ is not detected evenly at the surface.
(2) The light ray L1′ emitted by the light-emitting component 12 passes through air and then enters the transparent component 16. Next, after two total reflections and passing through the transparent component 16 once more, the light ray L1′ passes through air again and then arrives at the surface 31. According to the prior art, utilizing the lens 18, the light ray reflected by the surface 31 can be formed as an image on the sensor 24. That is, the reflected light ray passes through air, enters the lens 18, leaves the lens 18 and then goes into air again. Next, the reflected light ray enters a layer of a transparent silica gel on the sensor 24 (for protecting the sensor 24), and then arrives at the sensor 24. Therefore, the intensity of the light ray decreases each time when the light passes through an interface formed by different mediums, causing the direction of the light ray to become disordered.
(3) The transparent component 16 is utilized for transmitting the light ray that arrives at the surface 31 and for transmitting another light ray reflected by the surface 31 to the sensor 24. By this method, the effect of filtering out the noises is not good.
(4) The transparent component 16 is a light-pervious component. Several light rays L1′ and L2′ arriving at the surface 31 rather than the image formation area of the surface 31 will arrive at the sensor 24, causing unnecessary interference resulting in a situation in which the images sensed by the sensor 24 are blurred.
(5) The lens 18 can collect the reflected light rays from the image formation area of the surface 31 and transmit them to the sensor 24. The light illumination area is large, however, so many scattered light rays not from the image formation area may enter the sensor 24 through the transparent component 16, resulting in a situation in which the images sensed by the sensor 24 are blurred.